1. Field of the Invention
The present invention relates generally to a scanning probe microscopy apparatus and, more specifically, the present invention relates to a integrated circuit testing apparatus.
2. Background Information
One use for scanning force microscopes is to measure periodic electrical signal waveforms on or near a surface of a sample such as for example an integrated circuit. FIG. 1 is a block diagram illustrating a present day scanning force microscope 101. As shown in FIG. 1, the scanning force microscope 101 includes a probe 113 having a cantilever 115 positioned on or near a signal line 117 proximate to a surface 118 of a sample 119. An optical source 103 provides light 123 which is directed through a beam splitter 107, directed through a lens 109 and is reflected off a mirror 111 onto cantilever 115.
Cantilever 115 is coupled to receive a probe waveform that is used to measure the periodic electrical signal waveforms in signal line 117. The interaction between the periodic electrical signal waveforms in signal line 117 and the probe waveform in cantilever 115 causes periodic mechanical motion of cantilever 115 through the capacitive coupling between cantilever 115 and signal line 117. This mechanical motion is detected with detector 105 through light beam 123, which is reflected off cantilever 115 back off of mirror 111 through lens 109 and off of beam splitter 107 into detector 105. Alternatively, the cantilever 115 can directly contact the signal line 117 and directly couple the electrical signal from the signal line 117 to the cantilever 115 and eventually to the probe 113. From the probe 113, the signal can be coupled to any number of apparatuses, such as for example oscilloscopes, to measure the characteristics of the signal.
FIG. 2 is an illustration showing probe 113 and cantilever 115 of FIG. 1 in greater detail. As shown in FIG. 2, a fixed end of cantilever 115 is attached to a chip 201. Light 123 is directed to a back side of cantilever 115 and is reflected off of the back side. Motion of cantilever 115 is detected by observing light beam 123 after it has been reflected off the back side of cantilever 115.
Referring back to FIG. 1, it can be seen that a microscope objective lens 121 is used to observe and position cantilever 115 in relation to the surface 118 of sample 119. One disadvantage with present day scanning force microscope 101 is that mirror 111 partially obstructs the field of vision of microscope objective lens 121 when viewing and positioning cantilever 115.
Another disadvantage with the present day scanning force microscope 101 is that it is difficult to measure simultaneously two or more nodes in close proximity on the surface 118 of sample 117. In particular, since mirror 111 is positioned above cantilever 115 and protrudes beyond the free end of cantilever 115 as shown in FIG. 1, it is difficult to position more than one scanning force microscope to measure multiple signal waveforms in a small area of surface 118. More generally, in present day scanning probe microscopes employing optical deflection sensors, it is difficult to position two or more probes in close proximity due to the protrusion of the optical path used to sense cantilever motion beyond the end of the cantilever.